1. Field of the Invention
This Invention relates to a dual reciprocating bellows pump having dual cylindrical reciprocating bellows, which are capable of being expanded and contracted and defining pumping chambers for feed-to-pump fluid or pumped fluid such as semiconductor processing liquid, operating air being fed to the outside of the pumping chambers, and more particularly, to a dual reciprocating bellows pump, in which a pair of, i.e., left and right, bellows having the same structure are disposed on the opposite sides of a pump head and operated in an interlocked fashion by an interlock shaft means.
2. Description of the Prior Art
Dual reciprocating bellows pumps of this type are disclosed in U.S. Pat. Nos. 5,558,607 and 5,893,707. In these disclosed dual reciprocating bellows pumps, suction side and discharge side valve units are assembled as ball valve type unidirectional valves in a pump head disposed centrally of the pump, and a left side and a right side pumping chamber are defined by the pump head and pistons mounted on the movable ends of the left side and right side bellows, respectively. A left side and a right side operating air chamber for selectively feeding operating air thereto, are defined in the other regions of the bellows partitioned by the pistons. The pistons are mounted on the opposite ends of a single interlock shaft, and are used in unison therewith, whereby the left side and right side bellows undergo expansion and contraction to perform pumping operation.
In this construction, since the suction side and discharge side pump units are both assembled in the pump head, the size of the pump head, particularly the thickness or transversal size thereof, is inevitably large, thus posing a problem that it is difficult to design size reduction of the pump as a whole. In the case of using the pump as, for instance, a circulation pump for feeding semiconductor processing liquid, materials excellently corrosion- and chemical-resistant such as fluorine resins are desirably used for pump portions to be in contact with the liquid. Such materials are considerably expensive, thus leading to a demand for pump size reduction as much as possible for material expenditure saving. The above construction, however, can not sufficiently meet this demand.
In a different construction of the pertaining prior art pump, an interlock shaft means is movably disposed outside the pumping chambers, and the left side and right side bellows are coupled to the interlock shaft means for interlock operation to each other. In this case, however, it is necessary to provide a space for supporting the interlock shaft means and related structure part in the pump housing. Therefore, the size of the pump housing, and hence the size of the pump as a whole, is inevitably increased, and as in the above case the problem that it is difficult to reduce the pump size is posed.
The invention was made in view of the above various problems inherent in the prior art bellows pumps, and thus it is an object of the invention to provide a dual reciprocating bellows pump, which can facilitate size reduction design of the whole pump and reduce cost of manufacture by material expenditure saving.
It is another object of the invention to provide a dual reciprocating bellows pump, which can reduce the dead spaces in the pumping chambers to prevent undesired residence or stay of feed-to-pump fluid in the pumping chambers and also has improved self-suction performance.
To attain the above objects of the invention, the invention proposes a dual reciprocating bellows pump, in which a left side and a right side cylindrical bellows are sealedly mounted on the opposite sides of a pump head, end members are sealedly coupled to the other free ends of the bellows and define pumping chambers for feed-to-pump fluid or pumped fluid inside the bellows while also defining operating air chambers together with the outer side of the bellows and the pump housing, and interlock shaft means for interlocking the left side and right side bellows movably or slidably penetrates the pump head to project or extend into the left side and right side pumping chambers and be operatively engaged with the inner surfaces of the associated end members, thereby interlocking the two bellows for the performance of pumping operation.
The dual reciprocating bellows pump according to the invention particularly has a construction comprising a pump housing, a pump head assembled in the pump housing and having a suction port and a discharge port for sucking and discharging feed-to-pump fluid, respectively, a pair of, i.e., left side and right side, cylindrical bellows having stem portion sealedly mounted on opposite sides of the pump head and reciprocal in the pump housing with a predetermined stroke of expansion and contraction along the longitudinal axis of the pump housing, end members each sealedly coupled to the free end of each of the bellows and co-operative with the bellows to define a pumping chamber inside the bellows and also define an operating air chamber together with the bellows and pump housing; an operating air feed-in means communicating with the left side and right side operating air chambers provided in the housing for selectively feeding operating air to either of said paired operating air chambers, interlock shaft means interlocked to the reciprocation of one of said paired bellows for causing reciprocation of the other bellows, suction side valve units mounted on the pump head and each disposed as a unidirectional valve between said suction port and each pumping chamber for allowing in-flow of feed-to-pump fluid from the suction port to the pumping chamber, and discharge side valve units mounted on the pump head and each disposed as a unidirectional valve between said discharge port and each pumping chamber for allowing out-flow of the feed-to-pump fluid from the pumping chamber to the discharge port; said valve units each having a valve case and a valve member movably supported therein;
wherein: said valve cases of the suction side and discharge side valve units are disposed below and above a center of the cross-section of the cylindrical bellows and project into the associated pumping chamber; said interlock shaft means is constituted by a pair of interlock shafts movably penetrating the pump head in the longitudinal axial direction, and each of said interlock shafts having one end projecting in one of the pumping chambers and operatively engaged with the inner surface of the associated end member and the other end projecting in the other pumping chamber and operatively engaged with the inner surface of the associated end member, the two interlock shafts being disposed at a left side and a right side position, respectively, spaced apart from the center of the cross-section of the cylindrical bellows.
In the above arrangement according to the invention, the pair of interlock shafts constituting the interlock shaft means and projecting via the pump head into the left side and right side pumping chambers, are disposed at positions spaced apart to the left and right, respectively, from the center position of the bellows, and the valve cases of the suction side and discharge side valve units are disposed below and above the center and project into the pumping chambers. The two valve cases and the interlock shafts thus greatly contribute to the solution of the problem of the so-called xe2x80x9cdead spacesxe2x80x9d in the pumping chambers. It is thus possible to reduce the phenomenon of undesired residence or stay of feed-to-pump fluid in the pumping chambers as much as possible and obtain improved self-suction performance.
Also, since the two valve cases are not assembled inside the pump head, it is possible to reduce the thickness or transversal size of the pump head. Furthermore, since the paired interlock shafts are disposed at the positions spaced apart to the left and right from the center position of the bellows, it is possible to facilitate size reduction design of the whole pump and also reduce material expenditures of synthetic resins or the like of the pump so as to permit pump manufacture at reduced cost. Still further, since the valve size can be increased as much as possible, it is possible to provide a highly efficient pump with reduced pressure loss.
Further, since the paired interlock shafts are provided as the interlock shaft means, unlike the single interlock shaft, in which forces pushing the end member of the associated bellows are concentrated at one point thereby to exert excessive force onto the end members, the pushing forces are distributed, and it is thus possible to prevent such excessive force onto the end members thereby to reduce the thickness of the end members for correspondingly saving material expenditures and permitting ready coping with faster operation owing to the bellows weight reduction.
In another preferred arrangement of the present invention, the invention seeks to provide a dual reciprocating bellows pump, which, regarding the valve cases of the suction side and discharge side valve units disposed one below the other, each valve case of each discharge side valve unit is disposed at an upper position while each valve case of each suction side valve unit is disposed at a lower position spaced apart by a distance along the vertical axis passing through the center noted above. Also, the paired interlock shafts are disposed in line symmetry with respect to the transversal axis passing through the center, and the distance noted above is set to be less than the diameter of the interlock shafts.
With the above arrangement, it is possible to further reduce the vertical size of the pump while providing a sufficiently large size of the combination of the upper and lower valve units. Besides, with the line symmetrical disposition of the paired interlock shafts, stabler pump operation is obtainable, because both interlock shafts can engage the corresponding end members in good balanced positions. Furthermore, with the discharge side valve units disposed at the upper position, air bubbles can be smoothly discharged from the pumping chambers.
In a further preferred arrangement of the present invention, the invention seeks to provide a dual reciprocating bellows pump, in which, concerning the operative coupling between the paired interlock shafts constituting the interlock shaft means and the end members of the associated bellows, the ends of the interlock shafts are in contact engagement with the inner surfaces of the end members.
With this arrangement, no particular means is necessary for mounting the interlock shafts onto the end members of the bellows, and also in the assembling of the interlock shafts in the pump, the assembling operation can be simply completed by merely inserting the interlock shafts through the pump head. Thus, it is possible to increase the efficiency of the assembling operation and reduce cost thereof.